StarDate Podcast

A recently discovered planet is facing its final days. It’s evaporating, leaving a trail of debris that stretches halfway along its orbit. The planet is known by a catalog number – BD +05 4868 Ab. It’s only the fourth evaporating planet ever seen. It orbits the main star in a binary system in Pegasus, which is in the eastern sky at nightfall. The star is smaller and fainter than the Sun, and more than twice the age of the Sun. The planet was discovered by TESS, a planet-hunting space telescope. The planet passes in front of its parent star once every 30.5-hour orbit, blocking some of the star’s light. But the dips in starlight are ragged and look different from orbit to orbit. That suggests the planet is shedding material, forming a lumpy trail. The planet is small, and it orbits the star at just two percent of the distance from Earth to the Sun. At that range, it’s heated to 3,000 degrees Fahrenheit. That vaporizes minerals at the surface. The vapor boils into space, where it cools and condenses to form solid grains. That creates a thick trail that extends both behind and ahead of the planet. As more of the planet vaporizes, its gravity weakens, allowing even more material to escape. So the planet could vanish entirely in as little as a million years. Astronomers will look at the system with Webb Space Telescope – revealing more details about this vanishing planet. Script by Damond Benningfield

The Sun isn’t bothered by much. That’s because it travels through the Milky Way on its own. But most of the stars in the galaxy have at least one companion star. And the interactions between them can have a big impact. Consider Spica, a bright star near the Moon tonight. Although it looks like a single star, it’s really at least two stars. One of them is more than 11 times the mass of the Sun, while the other is about seven times the Sun’s mass. That makes Spica one of the more impressive binary systems around. The stars are extremely close together. They follow a stretched-out orbit that brings their surfaces to within about 10 million miles of each other. So the stars have big effects on each other. For one thing, their mutual gravitational pull distorts both stars. They’re shaped like eggs, with the tapered end pointing toward the other star. Also, the pull of the smaller star appears to create ripples in the larger one. And the tapered end of each star is hotter than its opposite hemisphere. In a few million years, the larger star will explode as a supernova. That’s likely to blast away some of the gas at the surface of the companion. And it’ll probably send the smaller star zipping across the galaxy – fired into space by a close companion. Look for Spica to the right of the Moon early this evening. The fainter planet Mars is farther to the lower right of the Moon. Script by Damond Benningfield

Mars is dry, cold, and quiet. But that hasn’t always been the case. Billions of years ago it was much busier – and perhaps a comfortable home for life. Mars has had three major geological ages. The oldest was the Noachian. It’s named for a large highlands region in the southern hemisphere. It began about 4.1 billion years ago, and lasted for 400 million years. The solar system was still packed with big “leftovers” from the birth of the planets then. Many of them slammed into Mars, forming wide basins that are still visible today. At the same time, giant volcanoes belched gases into the atmosphere. That trapped heat, making Mars much warmer. Clouds might have produced rain or snow. The precipitation carved rivers and filled lakes and maybe even a large ocean. Conditions could have allowed the formation of microscopic life. At the end of that period, there were fewer impacts and less volcanic activity. Mars cooled off, and the water dried up. So Mars became quieter as the Noachian Age ended, and the next age began. Mars is close to the right or upper right of the Moon early this evening. It looks like a fairly bright star. But it’s quite low in the sky, especially as seen from the northern half of the country, so you need a clear horizon to spot it. The star Spica, which is about twice as bright as Mars, stands to the upper left of the Moon. We’ll have more about Spica tomorrow. Script by Damond Benningfield

Every pilot knows to check the weather before takeoff – no one wants to fly into a storm. And in the future, they might want to check the space weather as well. Storms on the Sun can interfere with technology here on Earth – including aviation technology. Solar storms are giant explosions of energy and charged particles. When these outbursts hit Earth, the effects can range from damaged satellites to power blackouts on the ground. Some radio frequencies can be blacked out as well. Scientists recently looked at the impacts on aviation. They studied tracking information for three small aircraft recorded during a massive solar flare in February of 2024. The aircraft automatically reported their position and other details to air traffic control and to other aircraft. The position information came from GPS satellites. But several times during the solar storm, the aircraft briefly lost touch, or they received bad position information. The problems were brief. But future storms could cause bigger problems. Bad information from GPS satellites, drops in radio links, and even radar blackouts could force flight controllers to rely on older methods to keep planes and passengers safe. That could cause delays and backups – or worse. So the researchers suggested that space weather briefings be developed for pilots – helping them safely navigate through space weather. Script by Damond Benningfield

As Earth was thawing out at the end of the last ice age, it was hit by a powerful blast from the Sun. The storm would have triggered spectacular displays of the northern and southern lights. And it left an imprint in tree rings. Using that imprint, scientists have found that the storm was the most powerful yet recorded. And they even have a time for the event: the first quarter of the year 12,350 BC. Solar storms pelt Earth all the time. Most of the storms are small. But big ones can damage or destroy satellites, zap power systems on the ground, and cause other mischief. The biggest one ever seen took place in 1859. It knocked out telegraph systems around the world. But scientists have found evidence of even bigger events in the more-distant past. Some of the events are recorded in tree rings. Charged particles from the storms interact with Earth’s atmosphere to produce a radioactive form of carbon. Trees take up some of the carbon, which decays to a more stable form at a known rate. So comparing the ratio of carbon isotopes in tree rings can tell us when big storms took place. Researchers measured the carbon in rings from the end of the ice age. And they developed a new model of chemistry of the atmosphere during such cold periods. Their work showed that Earth was hit by the strongest solar storm yet discovered more than 14,000 years ago. More about space weather tomorrow. Script by Damond Benningfield

If you watch the stars on a dark night, it’s easy to think of the sky as a great dome. But as the night goes on, the dome rotates. New stars rise in the east, while others disappear in the west. So ancient skywatchers thought of the sky not as a dome, but a sphere that completely encircles us – the celestial sphere. To the Greeks, the sphere was real – a perfect crystalline surface, with the stars hanging from it like lanterns. Earth stood still at the middle of the sphere, which turned around it. Today, of course, we know that Earth is turning, and the stars are so far away that they appear to be fixed in place. Yet astronomers still use the celestial sphere. Their coordinate system is based on it. The system has lines of latitude and longitude, an equator, and north and south poles – all of which are projections of Earth’s coordinates. The celestial poles, for example, are based on the projection of Earth’s poles – the directions in which our planet’s axis is pointing. There’s also a celestial equator – an extension of Earth’s equator. As darkness falls tonight, it arcs from Aquarius, in the east; through Aquila, in the south; and down to Virgo, in the west. Only those who live near the equator can see the entire celestial sphere. For everyone else, it’s clipped. And at the poles, only half of the sphere is ever visible – a great dome showing the same stars all year long. Script by Damond Benningfield

Many “open” star clusters arch high overhead on summer nights. They’re lined up along the glowing band of the Milky Way – the outline of our home galaxy. Each cluster is a family of stars – from a few dozen to a thousand or more. But open clusters don’t stay together for long. Their stars eventually spread out, so the cluster disappears. Some families begin to spread out early – before many of their stars are even fully formed. One recently discovered example is called Ophion. It consists of more than a thousand stars. Astronomers found the group by analyzing data from Gaia, a space telescope. They looked through observations of more than 200 million stars. Then they narrowed their search to stars that are cooler than the Sun, and no more than 20 million years old. And Ophion just popped out. The stars form a giant clump that’s centered about 650 light-years away. But all of its members are going their own way. So they don’t form an obvious “cluster” – a tight grouping that’s easy to pick out. Ophion is on the edge of a region that’s given birth to many thousands of stars. Exploding stars in that region – or within Ophion itself – might have scattered the stars like bowling pins, keeping the family from sticking together. Ophion is near the middle of Ophiuchus, which is well up in the south-southwest at nightfall. You can see many clusters there – but not a hint of the ill-fated Ophion. Script by Damond Benningfield

Human eyes are perfectly tuned to see sunlight. But that’s a thin slice of the total range of light. As a result, we miss a lot of what’s out there – even objects that are big and close. A recently discovered example is a cloud of gas and dust that’s been named Eos. It spans about 40 times the width of the Moon. But it’s thinly spread, and it produces most of its light in the far-ultraviolet – wavelengths we can’t see. And even if we could see them, Earth’s atmosphere blocks them. So Eos wasn’t discovered until astronomers combed through observations made two decades ago by a Korean space telescope. The cloud’s inner edge is about 300 light-years away. It’s along the rim of the Local Bubble – a giant void around the solar system that’s been cleared out by exploding stars. Eos is about 170 light-years across. It contains enough gas to make more than 5,000 stars as heavy as the Sun. But there’s no evidence that it’s ever given birth to any stars at all. And while it could spawn stars in the future, that’s not likely. The cloud is evaporating, and should vanish in about six million years. Eos is centered along the border between the northern crown and the head of the serpent. That point is high in the west-southwest at nightfall, to the upper left of the bright star Arcturus. But unless you have your own space telescope, there’s no way to see this giant neighbor. Script by Damond Benningfield

Many centuries ago, people knew of only seven metals. That also was the number of known “planets” – the five true planets that are visible to the naked eye, plus the Sun and Moon. So each metal was associated with a planet – gold with the Sun, silver with the Moon, for example. Another metal with a good match was quicksilver. It’s the only metal that’s liquid at everyday temperatures, so it was associated with the quickest planet: Mercury. And it was even given the planet’s name. The planet moves back and forth between the morning and evening sky every few months. That quick motion is where the planet got its name. Mercury was the Roman messenger god, who flitted across the heavens on winged heels. The only spacecraft to study the planet from orbit didn’t find any trace of the metal mercury on its surface. And if there’s any of it near the planet’s equator, it would go through all three everyday phases of matter. At night, the planet is so cold that the metal would be frozen solid. At noon, it’s so hot that it would vaporize, forming a gas. And for much of the rest of the daytime, it would be a liquid – quicksilver puddles on a quicksilver planet. Mercury will stand close to the Moon during the dawn twilight tomorrow. It looks like a fairly bright star, to the lower right of the Moon. The brighter planets Venus and Jupiter align to their upper right – the planets of copper and tin. Script by Damond Benningfield

Early risers are in for a treat tomorrow. Venus, Jupiter, and the twins of Gemini congregate around the Moon. The group climbs into good view a couple of hours before dawn. Venus is close to the lower right of the Moon, Jupiter is farther to the upper right, and Gemini’s twins are to the upper left of the Moon. The brighter twin, Pollux, is especially close to our satellite world. Venus is the “morning star” – the brightest member of the group after the Moon. It shines so brightly because it’s close to Earth and the Sun, and because it’s topped by clouds of sulfuric acid. They reflect about three-quarters of the sunlight that strikes them. Jupiter is the next brightest – mainly because it’s the largest planet in the solar system. It’s about 11 times the diameter of Earth, and it’s more than twice as massive as all the other planets and moons put together. And Earth is moving closer to Jupiter now, so the planet will grow even brighter over the next few months. Pollux and Castor, the twins, are true stars. But they’re hundreds of thousands of times farther than the planets, which dulls their countenance. Even so, they’re easy to see through the moonlight – part of a beautiful panorama in the early morning sky. Another bright light rises well below the group: Mercury, the Sun’s closest planet. The Moon will stand close to it on Thursday, and we’ll talk about that tomorrow. Script by Damond Benningfield

The crescent Moon will slide past three bright planets over the next three mornings, growing thinner as it does so. First up is Jupiter, the largest planet in the solar system. It looks like a bright star below the Moon at dawn tomorrow. The Moon is in the part of its orbit that carries it between Earth and the Sun. It’ll reach that point on Friday night. As it drops toward the Sun, the Earth-Moon-Sun angle changes. So the Sun lights up less and less of the lunar hemisphere that faces our way. As a result, the crescent gets thinner day by day. Tomorrow, for example, about 15 percent of the lunar disk will be in the sunlight. By Wednesday, as it poses near Venus, it’ll be down to eight percent. And by Thursday, when it’s close to Mercury, it’ll be the barest of fingernails – it’ll be daylight across only about three percent of the visible disk. On the other hand, as the crescent gets smaller, the dark portion of the Moon will get brighter. That’s because that part of the Moon is bathed in earthshine – sunlight reflected from our own planet. As the Moon gets thinner and thinner in our sky, Earth will get fatter and fatter in the lunar sky, so earthshine will get brighter. It’ll reach its peak when Earth is full – at the same moment that the Moon is new. The Moon will be lost in the Sun’s glare then, but it will return to view a couple of days later – as a thin crescent in the evening sky. Script by Damond Benningfield

For a few weeks in the spring of 1764, Charles Messier was a star-cluster-discovering machine. He found five globular clusters in Ophiuchus, the serpent bearer. He cataloged them as Messier 9, 10, 12, 14, and 19. Messier wasn’t interested in the clusters – or even in the stars. Instead, he was looking for comets. At the time, finding a comet was a way to fame and fortune. Kings offered prizes to those who found comets. And comets were named for their discoverers – a bit of immortality. But Messier and others kept coming across fuzzy objects that resembled comets. Figuring out if they really were comets wasted time. So the French astronomer decided to compile a catalog of these distractions. He logged more than a hundred objects. They included star clusters, galaxies, stellar nurseries, and the final gasps of dying stars. Today, Messier’s list is the most famous of all astronomical catalogs. The globular clusters all look about the same. They’re tight balls of stars. Today, we know that the typical globular contains a hundred thousand stars or more. And they’re among the oldest residents of the Milky Way – more than 10 billion years old. Ophiuchus is a large constellation that stands well up in the southern sky at nightfall. Messier’s globulars are scattered across it. They’re all visible through binoculars – just don’t mistake them for comets. Script by Damond Benningfield

Barnard 68 is one of the darkest objects in our section of the galaxy. It’s a small cloud that absorbs the light of the stars behind it, so it looks like a dark “hole” in the Milky Way. Before long, though, that void may shine with the warmth of newly forming stars. Barnard 68 is a Bok globule – a small, dark sphere of gas and dust. It’s about 500 light-years away, half a light-year wide, and about three times the mass of the Sun. It’s part of a complex of dark clouds that stands in front of the glowing band of the Milky Way. Barnard 68 is so dark because it’s quite cold – temperatures at its center are close to absolute zero. But that may be about to change. The globule has been stable for millions of years. But there’s evidence that it’s recently been hit by a cosmic “bullet” – a smaller clump of gas and dust. That appears to be causing Barnard 68 to collapse. As it collapses, the cloud will get denser and hotter, and perhaps split into several smaller clumps. Within a few hundred thousand years, the clumps could be well on their way to becoming new stars – glowing balls of gas born from a dark “hole” in the Milky Way. Barnard 68 is in Ophiuchus, the serpent bearer, which is in the southern sky at nightfall. The Milky Way runs through a corner of the constellation. Several clouds darken the Milky Way – birthplaces of future stars. Script by Damond Benningfield

The gods of ancient Greece had complicated relationships. As an example, consider Ophiuchus. He’s represented by a constellation that passes across the southern sky on summer evenings. The constellation represented Asclepius, the god of medicine and the son of the god Apollo. In one version of the story, Asclepius killed a snake with his staff. But another snake dropped some herbs on the dead one, bringing it back to life. Asclepius then used those herbs to resurrect the son of King Minos. Business was so good for Asclepius that fewer people were entering the underworld. So Hades, the god of the underworld, complained to Zeus, the king of the gods. Zeus then killed Asclepius with a lightning bolt. But that didn’t sit well with Apollo. To appease him, Zeus placed Asclepius in the sky. Today, those stars are known as Ophiuchus, the serpent bearer. He’s depicted with a snake wrapped around his waist. And that’s why the symbol for modern medicine is a pair of snakes wrapped around a staff – it represents the story of Ophiuchus. Look for the serpent bearer high in the south as night falls. Its stars are faint. Under a dark sky, though, they form a pattern that resembles a coffee urn. It stands upright in early evening, but lies on its side later on. The constellation’s brightest star is at the top of the coffee pot – the “head of the serpent bearer.” More about Ophiuchus tomorrow. Script by Damond Benningfield

Earth has something in common with Titan, the largest moon of Saturn. They’re the only two bodies in the solar system with liquids flowing and ponding on the surface. In the case of Earth, that liquid is water. But on frigid Titan, it’s liquid hydrocarbons – methane and ethane. Titan is the second-largest moon in the solar system – a bit bigger than the planet Mercury. Its surface is extremely cold – hundreds of degrees below zero. Its atmosphere is thicker than Earth’s, and it’s topped by a dense layer of smog. The Cassini spacecraft used radar to peer through the clouds. And its findings were remarkable. It discovered rivers flowing across the surface, emptying into lakes and seas. It also found clouds, which occasionally produce rain. Everything we can see on Titan contains a lot of carbon-based compounds – some of the raw building blocks of life. That’s led to speculation that Titan might have the precursors to life – or even life itself – hidden in a giant ocean below the crust. To be clear, there’s no evidence of life. But future missions to Titan will sniff around for such evidence – perhaps adding to the list of things that Earth and Titan have in common. Saturn appears quite close to our own moon tonight. It looks like a bright star to the lower left of the Moon as they climb into good view, by about 11 o’clock. But you’ll need a small telescope to pick out Titan. Script by Damond Benningfield

One of the best-known meteor showers will be at its best the next couple of nights. Unfortunately, the gibbous Moon will be in the sky during the best hours for meteor watching. That will spoil the view of all but the brightest meteors. Perseid meteors are spawned by Comet Swift-Tuttle. The comet orbits the Sun once every 133 years or so. As it plies the interplanetary space lanes, it sheds tiny bits of rock and dust. The grains spread along the comet’s path. Earth flies through this path every August. The particles ram into the atmosphere at more than 130,000 miles per hour. They heat the air in front of them to thousands of degrees, forming the glowing streaks known as “shooting stars.” Swift-Tuttle is an especially big comet – about 16 miles in diameter. And its orbit sometimes brings it close to Earth. In August of 2126, for example, it’ll pass just 14 million miles away. And about 900 years later, it’ll miss by just one million miles. It’s hard to project the comet’s orbit more than a few thousand years into the future. So it’s possible that it could someday hit Earth – a collision that would wipe out most of the life on our fragile planet. Perseid meteors are best seen between midnight and dawn. Find a safe viewing site away from city lights, block out the Moon as much as you can, and scan the sky for the celestial fireworks. Script by Damond Benningfield

Social media may go wild the next few days – filled with reports of UFOs in the early morning sky. Ignore them. The objects are fully identified. They’re the planets Venus and Jupiter – the brightest objects in the night sky after the Moon. They’re crossing paths, as Jupiter pulls away from the Sun as seen from Earth, and Venus drops toward it. Venus is the brighter of the two. Venus and Jupiter could have a big influence on our own planet – not astrologically, but gravitationally. The planets all probably moved around a lot when the solar system was young. Today, their configuration is stable. And it should remain stable for hundreds of millions of years. But it’s impossible to predict beyond that. Tiny differences in a planet’s current orbit could have a big impact on its position in the far distant future. As a planet moves toward or away from the Sun, its gravity pushes and pulls the other planets, changing their location. Earth is most influenced by the gravity of Venus – which passes closer to us than any other world – and Jupiter – the most massive planet. They squeeze and stretch Earth’s orbit over a cycle of about 400,000 years. In the distant future, they could destabilize the orbit – dramatically changing Earth’s place in the solar system. Look for these “influential” planets beginning a couple of hours before sunrise. They remain visible deep into the dawn twilight. Script by Damond Benningfield

Based on how bright the stars look to our eyes alone, Deneb ranks among the 20 brightest stars in the night sky. Because the stars are at different distances, though, that ranking is a little misleading. If we could arrange them based on their true brightness, Deneb would outshine them all. In fact, it might be the brightest of all the stars that are easily visible to the unaided eye. Deneb is high in the east-northeast at nightfall, at the lower left corner of the bright Summer Triangle. Deneb is a blue supergiant – it’s much bigger, heavier, and hotter than the Sun. And it’s much, much brighter. Exactly how much brighter isn’t certain. That’s because there’s disagreement about the star’s distance. Astronomers have measured the distance with several techniques. Some are more direct, while others are based on models of different types of stars. That’s yielded estimates of about 1400 to 2600 light-years. And that makes a big difference. At the greater distance, Deneb would be almost four times brighter than at the smaller one. So Deneb’s true luminosity – the value when you add up all wavelengths of light – is somewhere between 50,000 and 200,000 times the Sun’s. If the high end of that range is correct, then Deneb is one of the brighter stars in the entire galaxy – and perhaps the brightest star that’s easily seen with the eye alone. Script by Damond Benningfield

Altair is a close neighbor – just 16.7 light-years away. Only about 50 star systems are closer. And it’s bigger and brighter than the Sun, so it’s easy to study. Even so, not even the largest individual telescopes can see it as more than a bright dot. Yet astronomers have managed to take a fairly detailed picture of it. They’ve done so with a technique known as interferometry. It combines the views from several fairly small telescopes that are linked together. That reveals as much detail as a single giant telescope. Just how much detail depends on the number and size of the telescopes, and how far apart they’re spaced. The setup doesn’t necessarily see fainter stars and galaxies, but it does see the universe with greater clarity. With conventional telescopes, astronomers had found that Altair spins in a hurry – once every eight hours, versus about 25 days for the Sun. That suggested the star was flattened. They measured that flattening with an interferometer; the star is about 25 percent wider through the equator than through the poles. A few years later, they confirmed that it’s cooler and darker around the equator. And in 2006, they even took a picture of Altair – the first detailed image of any Sun-like star. Altair is high in the southeast at nightfall, at the lower right corner of the bright Summer Triangle. We’ll talk about another member of the triangle tomorrow. Script by Damond Benningfield

A bright Moon is a beautiful sight – unless you have your heart set on seeing the stars. In that case, it’s a pest. The Moon’s glare overpowers many of the stars in the sky. But some manage to shine through even the brightest moonlight. Tonight, for example, even though the Moon is about 95 percent full, three stars are quite easy to find: Vega, Deneb, and Altair – the Summer Triangle. The triangle stands high in the eastern sky at nightfall, and climbs directly overhead later on. Its brightest member is Vega, at the top of the triangle. It’s about 25 light-years away. That means the light you see from the star tonight began its trek across the galaxy in the year 2000. Vega is bigger and heavier than the Sun, and almost 50 times brighter. Deneb is to the lower left of Vega. Its distance is uncertain; more about that tomorrow. What is certain is that it’s a supergiant – many times bigger and more massive than the Sun, and tens of thousands of times brighter. And its fate is pretty well known, too: Deneb is likely to explode as a supernova sometime in the next few million years. Altair is farther to the lower right of Vega. It’s the closest member of the triangle – just 17 light-years away. It’s a lot like Vega, just not quite as impressive. Still, it’s easy to spot through the moonlight – a member of the bright Summer Triangle. Script by Damond Benningfield

The universe follows a set of rules – the laws of physics. Those laws govern everything from the vibrations of the strings on a cello to the motions of the stars and planets. In fact, for centuries it was thought that the stars and planets must produce their own heavenly music – the music of the spheres. The idea was first proposed about 2500 years ago, by Pythagoras of Samos. The Greek philosopher studied the music produced by a lyre – a small, handheld harp. Its tones were produced by the vibrations of the strings. He found a mathematical relationship between the tones and the length of the strings. Since the strings were vibrating, that meant they were moving. Pythagoras then suggested that everything that moves produces its own vibrations – its own music. And that included the heavens. At the time, the leading view of the universe said it consisted of a series of spheres. The Sun, Moon, and known planets were embedded in their own spheres. The stars were in the outer sphere. As the spheres moved, Pythagoras said they should produce musical notes. The relationships between the spheres determined the specific notes. Taken together, they should produce a beautiful cosmic harmony. Over the centuries, some thought the music was real. Others thought of it as more symbolic – an indication that the universe was in harmony – a different way to “hear” the music of the spheres. Script by Damond Benningfield

Many of us have our own muse – someone who’s inspired us in a profound way. Such people can be seen as the descendants of the original Muses – goddesses who inspired great accomplishments in music, dance, poetry – and astronomy. The Muses were the daughters of Zeus, the king of the gods of Olympus, and Mnemosyne, the goddess of memory. And they were the great grand-daughters of Uranus, one of the Titans – the gods who came before the Olympians. The Muse of astronomy was Urania – a name that means “heavenly.” She inspired people to look at the stars, to draw maps of them, and to create stories about them. She was also said to be able to see the future by “reading” the stars. In classical artworks, Urania often is shown looking skyward, and wearing a cloak that’s covered in stars. In some pieces, she also has a halo of stars. Because the stars were important for navigation and mapping in the ancient world, her symbols were a globe and a compass. In the 16th century, Danish astronomer Tycho Brahe named his observatory “Uraniborg” in her honor. A half-dozen other European observatories have also borne her name. And she’s in the official seals of the U.S. Naval Observatory and the Royal Astronomical Society of Canada. So the mythical Muse who inspired people to watch the sky in ancient Greece is still an inspiration today. Script by Damond Benningfield

The number of known “exoplanets” that might sustain life keeps going up – it’s in the hundreds. Such a planet is in the “habitable zone” of its parent star – the distance where conditions are most comfortable for life. That zone depends on the type of star. It’s close in for small, faint stars, but a long way out for stars that are big and bright. In fact, such stars might not even have a habitable zone. And if they do, it won’t last long. One example is Antares, the heart of the scorpion, which huddles close to the Moon tonight. Antares consists of two stars. The star we see is many times bigger and heavier than the Sun. And it’s probably 50,000 to a hundred thousand times brighter than the Sun or more. For a planet to receive the same amount of energy that Earth gets from the Sun, it would have to be at least 225 times farther out than Earth is. And at that distance, the second star in the system might make the planet’s orbit unstable. It might even kick the planet out of the system. Even if a planet did exist in the habitable zone, it wouldn’t last long. Antares is likely to explode in the next million years or so – a bad development for any planet. So if anything inhabits the Antares system, it’s probably just visiting – perhaps some scientists from another star system watching this impressive but unfriendly pair of stars. Script by Damond Benningfield

Mars appears to have a shadow this evening – a faint star with one of the more lyrical names in the heavens: Zavijava. Mars looks like a fairly bright orange star, quite low in the west as darkness falls. Zavijava is almost touching it. It’s a good bit fainter than Mars, though, so you might want to use binoculars to enhance the view. Zavijava is a pretty close neighbor. According to the Gaia space telescope, it’s just 35.88 light-years away. Only a few dozen stars that are visible to the unaided eye are closer. The star’s name comes from an Arabic phrase that means “corner of the barking dog.” But Zavijava isn’t related to any of the dogs in the night sky. Instead, it’s one of the brighter stars of the constellation Virgo, so it’s also known as Beta Virginis. Zavijava is a little bit bigger and heavier than the Sun. It’s younger than the Sun by roughly one-and-a-half billion years. But because of its greater heft, it’s already nearing the end of the main phase of life. Before long – on the astronomical timescale – it’ll undergo a series of changes in its core. That will make the star much bigger and brighter. It will remain in that phase for hundreds of millions of years. Over the past few decades, astronomers have reported the discovery of several possible planets around the star. None of those reports has stood up. But the search continues – for worlds orbiting Zavijava. Script by Damond Benningfield

For a star, passing too close to a black hole is never a good thing. If the star doesn’t get eaten, it can get kicked into a high-speed jaunt across the cosmos. And astronomers can track the path of such a star back to its birthplace. One such high-speed star is plowing through the galaxy at more than a million miles per hour. Today, it appears near the twins of Gemini. But it may have been born halfway across the sky, in Pegasus. When astronomers traced the star’s path, they found that it intersected with the star cluster Messier 15 about 20 million years ago. The star is the same age as the stars in the cluster, and it has the same composition. That suggests the star was born in M15, then booted out – probably by an encounter with a black hole more than a hundred times the mass of the Sun. Other astronomers had reported the possibility of such a black hole more than 20 years ago. And the high-speed star appears to confirm it. Originally, the star would have been a member of a binary. But the two stars passed close to the black hole – closer than Earth is from the Sun. In a complex gravitational dance, the binary was ripped apart. One star was gobbled up by the black hole. But the other one got away – beginning a high-speed dash across the galaxy. Today, the star is more than 37,000 light-years from the cluster – a possible survivor of a close encounter with a black hole. Script by Damond Benningfield

A small star with a planetary companion appears to be making a high-speed exit from the center of the Milky Way – perhaps fast enough to escape the galaxy entirely. The system is more than 24,000 light-years away, in Sagittarius. It appears to contain a red-dwarf star – a cool, faint ember about 20 percent the mass of the Sun. It’s accompanied by a “super-Neptune” – a planet about 30 times the mass of Earth. They’re separated by less than the distance from Earth to the Sun. What makes the system especially interesting is its high speed – at least 1.2 million miles per hour. That’s not fast enough to leave the Milky Way behind. But it could be moving a good bit faster. The system might have started as a member of a binary – two stars bound by gravity. The stars passed too close to the monster black hole in the galaxy’s heart. The black hole grabbed the other star, and gave the escapee a giant kick. On the other hand, the kick could have come from an encounter with a smaller black hole in the Milky Way’s crowded center. How the star maintained its grip on the planet is a key question. But the planet must have been in a tight orbit to avoid being yanked away. Researchers were scheduled to take some follow-up observations this month. That might reveal whether the system really is a star and planet on a high-speed ride through the galaxy. We’ll talk about another possible escapee tomorrow. Script by Damond Benningfield

The supermassive black hole at the heart of the Milky Way is never quiet – it’s constantly popping off. The black hole is more than four million times the mass of the Sun. It grabs passing gas clouds, asteroids, and other objects. It also sponges up gas from the “winds” produced by nearby stars. This forms a swirling disk around the black hole. As material spirals inward, it gets extremely hot. Astronomers watched the black hole with James Webb Space Telescope. They found that it produces several bright outbursts every day, with each one lasting an hour or longer. Between these outbursts there were fainter flares that usually lasted less than a minute. The flares may have different causes. Shorter flares may be caused by turbulence in the disk, which squeezes and heats pockets of gas. Particles bounce around inside these pockets, heating up and producing outbursts of energy. The longer flares may explode when magnetic fields twist together, then snap. That produces big outbursts of particles and energy like the giant flares on the Sun. The astronomers hope to take an even longer look at the system, helping them learn more about the constant flare-ups from the Milky Way’s monster black hole. The black hole is in Sagittarius. The constellation is in the south on summer evenings, and forms the outline of a teapot. The black hole is immersed in the “steam” above the spout – 26,000 light-years away. Script by Damond Benningfield

Sagittarius marks the center of our home galaxy, the Milky Way. So the constellation is packed with stars, star clouds, and star clusters. But one of the clusters doesn’t belong to the Milky Way at all – at least not yet. It’s in a small, puffy galaxy on the far edge of the Milky Way’s disk. Messier 54 is a globular cluster – a ball-shaped region about 150 light-years across, packed with hundreds of thousands of stars. Native globulars are among the Milky Way’s oldest residents – they were born with the galaxy itself. But a few of the clusters were born in other galaxies, then absorbed when their home galaxies were absorbed by the Milky Way. For a long time, astronomers thought that M54 was a charter member of the Milky Way – one of its early globular clusters. A couple of decades ago, though, they found that it’s near the center of a newly discovered galaxy, the Sagittarius Dwarf. That puts it outside the Milky Way’s disk. But the Milky Way is pulling the smaller galaxy in. Eventually, it will incorporate all of the galaxy’s stars. So M54 will become a member of the Milky Way – one of its newest residents – and one of its oldest. Sagittarius scoots low across the south on summer nights. It looks like the outline of a teapot. M54 is at the lower left corner of the teapot, but you need a telescope to see it. Script by Damond Benningfield

Mars won’t exactly roll out the red carpet for human explorers. In fact, the Red Planet could be deadly. It’s bitterly cold, the air is too thin to breathe, there’s no ozone layer to block the Sun’s ultraviolet rays, and there’s no magnetic field to deflect solar storms. And if that’s not enough, there’s one more potential hazard: dust. A recent study said the dust could damage lungs and other organs and cause nasty diseases. Dust covers much of the planet, giving Mars its orange color. It’s easily lofted by the wind, and dust storms can blanket much or all of the planet. Researchers studied the dust, along with problems that Apollo astronauts experienced with Moon dust. They found that the Mars dust grains are too small to be filtered out by the lungs. Instead, they’d enter a person’s bloodstream. Not only are the grains abrasive, but the dust contains high levels of some nasty compounds. So the dust could cause everything from thyroid problems to a condition similar to black-lung disease. Some ailments could be treated on Mars. But any serious problems might require help from Earth – a journey of months. So Mars travelers will need good air filters, self-cleaning spacesuits, and other methods to protect them from the deadly sands of Mars. Mars stands close to the crescent Moon as darkness falls this evening. It looks like a fairly bright star – a hazardous destination for human explorers. Script by Damond Benningfield

Astronomers generally don’t play many official practical jokes. But an Italian astronomer played one more than two centuries ago. And the joke is still there for everyone to see. It’s in Delphinus, the dolphin. The constellation is small and fairly dim. But five of its stars form an outline that really does resemble a dolphin, making it easy to find. It’s a third of the way up the eastern sky at nightfall, with the dolphin’s tail on the right and its snout on the left. The brightest members of the outline are Beta and Alpha Delphini. Beta is a binary – two stars bound by their mutual gravitational pull. Both are bigger, brighter, and heavier than the Sun. Alpha consists of three stars. All of them are more impressive than the Sun, with the main star almost four times the mass of the Sun. The stars also have proper names. Beta is known as Rotanev; Alpha is called Sualocin. And that’s where the joke comes in. The names first appeared in 1814, in an atlas published by the director of the Palermo Observatory. The names caught on, but their origin was a mystery. It was solved by a British astronomer 45 years later. He realized that the observatory’s assistant director at the time was Niccolo Cacciatori. In English, the name would be Nicholas Hunter; in Latin, Nicolaus Venator. Spell the Latin names backwards, and you come up with Sualocin and Rotanev – a little joke among the stars of the dolphin. Script by Damond Benningfield

Zeta Tauri is the kind of star that few of us really notice. It’s at the tip of one of the horns of Taurus, the bull. But it shines at only third magnitude. That’s no problem under dark skies, but tough to see from a light-polluted city. It’ll be much easier to find before dawn tomorrow, though, because it’ll stand just a whisker from Venus, the brilliant “morning star.” Zeta Tauri is actually two stars, not one. They’re separated by a bit more than the distance from Earth to the Sun. But at the system’s distance of about 440 light-years from Earth, it’s impossible to see them as individual stars, even with the largest of telescopes. In fact, it’s tough to even learn the nature of the two stars. One of the stars is easy to figure out. It’s about 11 times the mass of the Sun, five times wider than the Sun, and thousands of times brighter. But its companion isn’t fully understood. It may be a white dwarf – a stellar corpse as heavy as the Sun. The main star is blowing a strong wind of gas into space. That’s formed a cloud around the star. The white dwarf may pull in some of that material. As it piles up on the white dwarf it gets much hotter, making the system a strong source of X-rays. In the next few million years, the heavier star of Zeta Tauri is likely to explode as a supernova. That’ll make it impossible to overlook this currently meager star. Script by Damond Benningfield

Water, water everywhere, nor any drop to drink. The line from “The Rime of the Ancient Mariner” is true not only on Earth, but across the solar system. Water is everywhere. But it’s not in a form you could drink. It’s in the clouds of the giant outer planets, frozen in the surfaces and ice caps of planets and moons, or buried far below their surfaces. One example is Pluto. The dwarf planet is billions of miles from the Sun, so its surface is frozen. But there’s evidence that liquid water lurks far below. In fact, there could be a global ocean up to a hundred miles deep. One bit of evidence is a feature called Sputnik Planitia – a fairly smooth plain about 600 miles across. It’s almost pure white. And there are no impact craters, suggesting that the surface is young. Among its features are floating blocks of frozen gases. They resemble slabs of ice in the polar regions of Earth. That suggests they could be floating atop liquid water. Plumes of water flow upward, freezing and pushing older ice outward. In fact, the feature might have formed when a big asteroid slammed into Pluto. It vaporized the surface, exposing the ocean below. The water quickly froze, forming the plain we see today. Pluto lines up opposite the Sun this week. It’s in view all night, and shines brightest for the whole year. Script by Damond Benningfield

The east coast of Florida first heard the roar of a rocket heading toward space 75 years ago today. It failed. But it set the stage for thousands more launches – payloads intended for Earth orbit, the Moon, and targets throughout the solar system. The military had been conducting test flights from White Sands, New Mexico. But it was limited by the land-locked site. So it turned to a piece of scrubland known as Cape Canaveral. The site was chosen because it was isolated, it offered a moderate climate, and it was close to the equator, so it gave east-bound rockets an extra kick. Most important, it offered tens of thousands of square miles of open ocean to catch falling rockets. So workers carved out some space and built several launch pads. And on July 24th of 1950, they put one of them to work, launching a rocket called Bumper 8. The first stage was a V-2 captured from Germany at the end of World War II. The second stage was a small American-built rocket. As often happened in the early days, something went wrong. The rocket followed the wrong path, causing the second stage to fail. A second Bumper launch, nine days later, fared a bit better, but still didn’t achieve all of its goals. Today, Cape Canaveral and the adjoining Kennedy Space Center are busier than ever. Last year, they hosted a record 93 launches – adding to the tally of a 75-year-old spaceport. Script by Damond Benningfield

A big storm on the Sun in May of 2024 caused big trouble for satellites. And they could face even bigger troubles in the coming decades. The storm was an especially powerful outburst of energy and particles. When the storm hit Earth, it heated the outer atmosphere, causing it to expand. That increased the drag on satellites in low orbit, causing them to lose altitude. A study put the average drop at about 600 feet per day – the length of two football fields. The satellites had to fire their thrusters to stay where they belonged. The study said that thousands of satellites had to execute those maneuvers – up to 5,000 per day. It was impossible to calculate all those maneuvers at once, so the risk of collisions went way up. No impacts were reported. But the number of satellites continues to skyrocket. And another study forecasts that the Sun should get even stormier over the next 40 years or so. The Sun goes through an 11-year cycle of magnetic activity. But there’s also a cycle of cycles. The average level of activity goes down for four or five cycles, then goes up for the next four or five. The study says we’ve reached the bottom of that “super” cycle, and should be on the way up. That means more big storms from the Sun, and more maneuvering by satellites – increasing the risk of collisions in low Earth orbit. Script by Damond Benningfield

Jupiter’s Great Red Spot is one of the most intriguing features in the solar system. It’s a storm that’s big enough to swallow Earth – but getting smaller. Winds at its perimeter blow much faster than any hurricane on Earth. And it has a bright reddish orange color. Despite a century and a half of study, though, it’s still mysterious. Scientists don’t know why it’s red, why it’s getting smaller, or how it fired up in the first place. They do know that the storm drifts westward around the planet. And a recent study found that it “inches” along like a garden slug. Scientists monitored the storm for three months with Hubble Space Telescope. They already knew that the Great Red Spot goes through a 90-day cycle. But this was the first time they plotted the changes in detail. The images revealed that the spot stretches and squeezes as it moves. When it’s moving slowest, it’s stretched out. When it’s moving fastest, it’s more compressed, so it’s a little rounder. The storm’s width varies by about a hundred miles, and its height by a bit more. The spot’s average width is more than 8,000 miles. That’s only a third the size when it was first seen. No one knows whether it will continue to shrink – and eventually disappear. Look for Jupiter close to the right of the Moon in tomorrow’s dawn twilight. It looks like a bright star. But it’s so low that you need a clear horizon to spot it. Script by Damond Benningfield

The three brightest objects in the night sky team up during the early morning twilight tomorrow: the Moon and the planets Venus and Jupiter. Venus is the “morning star,” to the upper right of the Moon. Slightly fainter Jupiter is to the lower left of the Moon. It’s quite low, so you need a clear horizon to spot it. Venus and Jupiter are siblings – they were born from the same disk of material around the newborn Sun. So were Earth and the solar system’s other planets. Besides their parentage, though, Venus and Jupiter don’t have a lot in common. Venus is a ball of rock a little smaller than Earth. It’s topped by clouds of sulfuric acid. They reflect most of the sunlight that strikes them, which is one reason Venus is so bright. Another is its proximity: Venus is the second planet from the Sun, while Earth is the third. So Venus passes closer to us than any other planet. Because Venus and Earth formed so close to the Sun, they’re made mainly of rock and metal. The young Sun blew away most of the lighter materials – gas and ice. So Venus is dense and heavy. Jupiter formed much farther from the Sun, where it was much colder. It built a big core of heavy materials, then swept up a lot of gas, dust, and ice. It became the largest planet in the solar system – a dozen times the diameter of Venus, and almost 400 times its mass – the “big brother” to the rest of the planets. More tomorrow. Script by Damond Benningfield

Since the start of the Space Age, we’ve learned a lot about the other planets of the solar system. But perhaps we’ve learned the most about Venus. That’s a bit of a surprise when you consider that Venus passes closer to Earth than any other planet. Venus is the brilliant “morning star.” It lines up close to the crescent Moon before dawn the next couple of days. Venus looks so bright in part because it’s blanketed by clouds that hide the surface. And that’s the main reason we’ve had so much to learn about the planet. Without any landmarks to go by, astronomers couldn’t even tell the length of the planet’s day. They didn’t figure it out until the early 1960s. They used radio telescopes to bounce waves off the surface. The echoes revealed that a day on Venus lasts 243 Earth days. For a long time, scientists thought the clouds were made of water vapor, just like the clouds on Earth. That led to speculation that Venus was warm and wet, with giant oceans and dense jungles. Instead, the clouds are made of sulfuric acid. And they hide a surface that’s hot enough to melt lead, with not a drop of water. Today, planetary scientists are still learning about Venus. It appears to be volcanically active, for example – perhaps one of the most active worlds in the solar system. So, many more surprises could lurk below the clouds of our brilliant neighbor. Script by Damond Benningfield

The Moon and the Seven Sisters huddle up in the wee hours of tomorrow morning. The Moon will “occult” the sisters – the brightest stars of the Pleiades star cluster. The stars form a tiny dipper that marks the shoulder of Taurus, the bull. Occultations have been useful scientific tools. The way a star vanishes, then reappears, can reveal details about both the star and the Moon. If the star fades in steps, that probably means it’s a binary – two stars that orbit each other. The Moon covers up one star a moment before it hides the second one. Several binary systems were discovered this way. Watching an occultation at different wavelengths also reveals details about the individual stars, such as their brightness and temperature. Occultations also have helped map the lunar surface. The Moon isn’t smooth – it’s marked by rugged impact craters, canyons, and mountains. The precise timing of the occultation reveals whether the star was blocked by one of these features. Occultations aren’t quite as important to scientists as they once were. But they’re still interesting to watch – as the Moon “hides” a star. This occultation will be in good view from the central and western parts of the United States, although it occurs a little late for most of the eastern part of the country. The exact timing depends on your location Script by Damond Benningfield

There are several ways to envision the celestial scorpion. The main way is to look for the outline of the scorpion, which is low in the south at nightfall at this time of year. Its curving body really does resemble the nasty little arachnids. Its head is to the upper right of the body, the tail and stinger to the lower left, with the bright orange star Antares between them. Then there’s the scientific way. Astronomers have divided the sky into 88 official constellations, including Scorpius. Each one has precisely defined borders. Scorpius, for example, is bounded by 18 facets. So the constellation looks a bit like an off-center tower of boxes. Finally, there’s the astrological way – the sign of Scorpio. It’s one of the signs of the zodiac – sections of the Sun’s path across the sky. About 2500 years ago, the astrologers of ancient Babylon split the zodiac into 12 signs, all of the same width. So the Sun spent roughly the same amount of time in each sign. It was “in” Scorpio from about October 23rd to November 21st. And at the time, that was a fairly close match to the physical pattern of the scorpion. Over the centuries, though, the dates at which the Sun appears in front of a given star pattern have changed. Today, the Sun enters Scorpius several weeks later than it did centuries ago. But the astrological signs have remained fixed – away from the constellations for which they’re named. Script by Damond Benningfield

Astronauts and cosmonauts have been sharing time in orbit for three decades. But their first mission together began much earlier, with the Apollo-Soyuz Test Project. An Apollo spacecraft linked up with a Soviet Soyuz capsule in 1975. The craft had launched on July 15th. First up were two cosmonauts aboard the Soyuz, followed by three astronauts aboard the final Apollo. And 50 years ago today, the two spacecraft came together. Cosmonaut Alexei Leonov congratulated astronaut Tom Stafford, who’d flown the docking. LEONOV: Well done, Tom. It was a good show! The space travelers stayed together for two days. They shook hands, conducted some maneuvers, did some experiments, and took part in a lot of ceremonies, including a phone call from President Gerald Ford. FORD: Your flight is a momentous event and a very great achievement, not only for the five of you, but also for the thousands of American and Soviet scientists and technicians who have worked together to ensure the success of this very historic and very successful experiment in international cooperation. It took years to get the next joint mission off the ground. But today, despite wars, upheavals, and political chaos, American astronauts and Russian cosmonauts continue to meet in space. Script by Damond Benningfield

An astronomical trio lines up low in the east at first light tomorrow. Two of its members are easy to pick out: Venus, the brilliant “morning star,” with the true star Aldebaran close to its right. But to see the third member, you need to pull out your binoculars. NGC 1647 is just to the right of Venus, much closer than Aldebaran is. It’s a star cluster – a tightly packed family of hundreds of stars. Most of the cluster’s details are a bit fuzzy, though. Estimates of its age, distance, and the number of stars vary by quite a bit. In part, that’s because the cluster is behind a cloud of dust, which absorbs some of its light. But it’s also because NGC 1647 hasn’t received a lot of attention. Measurements put the cluster’s distance at about 1800 to 2,000 light-years. One study said the cluster has at least 600 member stars, while another puts the number at 1300 or more. And estimates of its age range from about 120 million years to more than 260 million. Based on the structure of NGC 1647, it appears that no matter how old it is, it may not last much longer. The cluster may be losing its grip on the stars outside its dense core. The stars are being pulled away by the gravitational tug of the rest of the galaxy. Soon, many of them could drift away – leaving a much smaller family of stars. Tomorrow: shaking hands. Script by Damond Benningfield

If you ever find yourself floating above the clouds of Saturn, gazing upon the planet’s magnificent rings, you might feel like you need to get your eyes checked. Even at noon, when the Sun is highest in the sky, the view will look as dim as the minutes before sunrise or after sunset here on Earth. That’s because Saturn is almost 10 times farther from the Sun than Earth is. At that distance, the Sun shines only about one percent as bright as it does on Earth. And that presents some problems for spacecraft that travel to Saturn. For one thing, they can’t use solar power. They’d need huge arrays of solar cells, which would make a craft far too heavy and expensive. Instead, Saturn-bound missions are nuclear powered. For another, it’s hard to take good pictures. A craft has to leave the shutter open for a long time to properly expose an image. At the speeds a craft is moving, that blurs the shot. The solution is to turn either the camera or the entire spacecraft to stay focused on the target. No spacecraft are operating at Saturn now. The next one is scheduled for launch in a few years. It’ll ferry a small helicopter to Saturn’s big moon Titan – under the faint light of the distant Sun. Saturn appears near our own Moon early tomorrow. It looks like a bright star, standing just below the Moon at dawn. The planet fades from view as the sky brightens – under the full glory of the nearby Sun. Script by Damond Benningfield

Only about one in five Americans was born before the “Mars Era” – before the first spacecraft visited the Red Planet. That first encounter took place 60 years ago today, beginning six decades of Mars exploration. Mariner 4 was launched in late 1964. A sister craft had failed. And early Soviet efforts failed as well. That inspired jokes about a “great galactic ghoul” eating Mars-bound probes. Mariner 4 had eluded the ghoul for seven months. AUDIO: Then, July 14th: Encounter Day. This is Mariner control. All systems are green. And as this NASA film explained, they stayed green. AUDIO: The shutter is operating, the TV sees the planet, the recorder is working. Mariner skimmed just 6100 miles from Mars. It snapped 21 pictures. The images depicted a landscape of craters and volcanic plains. They made Mars look like a dead planet. Yet Mars exploration continued. Later missions revealed that Mariner 4 was unlucky – it scanned an unusually desolate strip. Today, we know that Mars has an active atmosphere. Ice lurks just below its surface. And it once was warm and wet, with rivers flowing across its surface, perhaps filling a giant ocean – making Mars a possible home for life. Today, a half-dozen orbiters and rovers are exploring the planet. And others are being planned – extending a legacy of exploration that began six decades ago. Script by Damond Benningfield

A brilliant “new” star blazed into view more than a thousand years ago. It’s the brightest star ever recorded, and may be the brightest ever seen by human eyes. Supernova 1006 first appeared in late April of the year 1006. For a few weeks it shined many times brighter than Venus, which is the brightest object in the night sky after the Moon. It was bright enough to see during the day, and remained visible at night for more than two years. It was recorded by cultures around the world. At the time, nobody knew what the star actually was. Today, though, we know it was a supernova. It formed in a binary system. At least one of the two stars was a white dwarf – a stellar corpse. It might have pulled gas from a living companion star. Or perhaps the companion was another white dwarf, and the two stars rammed together. Either way, a white dwarf was pushed beyond its critical weight limit. That caused a runaway nuclear explosion that blasted the star to bits. Debris from the blast continues to race outward at millions of miles per hour. Astronomers watch this debris, mainly in radio waves and X-rays, to learn more about the star and its demise. Supernova 1006 was along the border between the constellations Lupus and Centaurus. The spot is low in the south-southwest at nightfall. But the residue of this brilliant outburst has faded away. Large telescopes reveal only a colorful ribbon at the edge of the expanding bubble. Script by Damond Benningfield

A couple of bright cousins of Antares, the heart of the scorpion, skitter to its lower right on July evenings. They’re the brightest stars of Lupus, the wolf. The stars of Lupus originally formed part of the adjoining constellation Centaurus. But they were split off to form a new constellation a couple of thousand years ago. The wolf’s brightest stars are Alpha and Beta Lupi. Both stars belong to the Scorpius-Centaurus O-B association – a complex of stars and star-making ingredients that spans hundreds of light-years. The first stars in the association were born about 25 million years ago. Beta Lupi probably was one of those stars. Winds from the earliest stars, along with shockwaves from exploding stars, probably triggered a major round of starbirth about five million years later. And two more big rounds followed, spaced about five million years apart. Alpha Lupi probably was born during one of those peaks, no more than 20 million years ago. Alpha Lupi is about 10 times the mass of the Sun. So despite its young age, it’s nearing the end. It will explode as a supernova within the next few million years. Beta Lupi is a little less massive. So it might explode as well. But it’s possible that it faces a less dramatic fate, ending its life as a small, faint ember – a meek end for a mighty star. Lupus is quite low in the south at nightfall. You need to be south of about Dallas or Phoenix to see its brightest stars. More about the wolf tomorrow. Script by Damond Benningfield

Newly forming planetary systems are busy and messy. They contain disks of gas, ice, and dust that are broken into wide bands. The supply of dust is replenished by frequent collisions between “exocomets” – balls of ice and rock up to a few miles across. And the bands may be stirred by the back-and-forth shifting of newborn planets. There’s a similar band in our own solar system – the Kuiper Belt. It begins beyond the edge of Neptune, the outermost major planet, and extends billions of miles from the Sun. Because the solar system has been around for billions of years, the belt is quiet – there are few collisions and little stirring. Astronomers recently studied the bands in about 300 young star systems. They contain a lot of leftover debris from the birth of the planets. So collisions between larger bodies are much more frequent. The impacts blast out a lot of dust, feeding the bands. In many systems, there’s more than one band. Gaps between them might have been cleared out by orbiting planets. And the bands come in different sizes. Wider ones might have been “pumped up” as giant planets moved toward and away from the parent star. The gravity of those planets would have kicked many of the exocomets into different orbits, causing them to spread out. The study didn’t see any planets. But the configurations of the bands suggest the planets are there – taking shape in the busy space around young stars. Script by Damond Benningfield

When it comes to the night sky, what you see isn’t necessarily what you get. Consider Venus and Aldebaran, which are low in the east at first light. Venus is the brilliant “morning star.” Aldebaran stands directly below Venus, and shines just one percent as bright. But their apparent brightness is the only way in which Venus outranks Aldebaran. Venus is a planet in our own solar system – a little smaller and less massive than Earth. It’s so brilliant because it’s close to both Earth and the Sun, and because it’s covered in bright clouds. Aldebaran, on the other hand, is a true star – and an impressive one at that. It’s heavier than the Sun, about 45 times wider, and more than 400 times brighter. Compared to that, Venus is a bare speck – a flake of cosmic jetsam. Aldebaran is almost half a million times more massive and 5,000 times wider – so big that you could pack more than a hundred billion Venuses into its great bulk. So Aldebaran appears fainter than Venus only because of its greater distance – almost four million times farther than the morning star. Look for this mismatched pair beginning a couple of hours before sunrise the next few mornings. Venus will slide to the lower left, and will stand side by side with Aldebaran on Wednesday. They’ll pull apart after that, with Venus dropping a little lower in the sky day by day, and Aldebaran climbing a little higher. Script by Damond Benningfield

Thunderstorms generate what may be nature’s most impressive displays: lightning. And there’s plenty of it; lightning strikes Earth millions of times every day. Although lightning is common, it’s also mysterious. The electric fields inside clouds don’t appear to be strong enough to power lightning. So for the past 90 years, scientists have pondered whether it might have a cosmic origin – cosmic rays – particles that ram into Earth’s atmosphere at almost the speed of light. Many of them come from the Sun. But the most powerful come from exploding stars, the gas around black holes, and other powerful objects in deep space. When a cosmic-ray particle hits an atom or molecule in the upper atmosphere, it creates a shower of other particles. And it’s these particles that might then zip through clouds, creating lightning. A study published earlier this year seems to affirm this idea. Scientists studied a thunderstorm over New Mexico with a sophisticated array of radio antennas. They traced more than 300 strikes from beginning to end, at intervals of less than a thousandth of a second. Among other things, the radio waves revealed that the bolts weren’t moving the way they should if they’d been sparked by the clouds themselves. Instead, the lightning seemed to be triggered by something coming from beyond Earth: cosmic rays. Script by Damond Benningfield

If you throw a rock into a still pond, waves ripple outward. They jiggle the leaves and bugs on the surface, shaking things up a bit. And the same thing happens in the stars. In fact, a giant region of the sky is still feeling some “ripples” today. The Scorpius-Centaurus O-B Association contains many stars of classes O and B – the hottest and brightest stars in the galaxy. It spans hundreds of light-years, and contains thousands of stars. And more stars are being born there today. The association began as a massive cloud of gas and dust. About 20 million years ago, it produced a big “wave” of starbirth. Many of the newborn stars quickly exploded as supernovas. That outburst was the “stone” in the pond. Strong winds and shockwaves from the stars rippled outward. That triggered the birth of more stars in the surrounding cloud. The rate of starbirth peaked about 15 million years ago. But the ripples didn’t stop. They created a smaller outburst about 10 million years ago, and another about five million years ago. Most of the stars in the region are no bigger than the Sun. But a few are big, heavy, and bright – monster stars born from the ripples in a galactic pond. Many of these monsters are in Scorpius, which is low in the south at nightfall, to the right of the Moon. It’s marked by the scorpion’s bright “heart,” the star Antares – the most prominent member of the Scorpius-Centaurus Association. Script by Damond Benningfield

The star that marks the heart of the scorpion is at death’s door. Sometime in the next million years or so, Antares is expected to explode as a supernova. But astronomers don’t know exactly when that’ll happen. There’s no way to see into its core, which is where the fusion reactions that power the star take place. And with current technology, we can’t tell that the end is near by looking at the surface of Antares. The star is many times the mass of the Sun, so when its nuclear engine shuts down, its core will collapse to form a neutron star or black hole. Its outer layers then will blast outward at a good fraction of the speed of light. But the star is so big that the shockwave won’t reach the surface for many hours, so it won’t begin to brighten for hours. The shockwave is powered in part by neutrinos – particles created during the collapse. They almost never interact with other matter, so most of them will zip through the star at almost the speed of light. But there are so many of them that the rare times they do interact will help drive the blast. As the neutrinos race through the galaxy, they’ll reach detectors on Earth hours before the surface of Antares begins to brighten – alerting us to the brilliant demise of a giant star. Antares stands to the upper right of the Moon at nightfall, and leads the Moon down the southwestern sky later on. We’ll have more about the scorpion tomorrow. Script by Damond Benningfield

The Moon will step on the head of the scorpion tonight. It will pass directly in front of one of the stars that outlines the head, blocking it from view – an event called an occultation. Pi Scorpii is actually a system of three stars, about 600 light-years away. The main star in the system is about a dozen times the mass of the Sun, and more than 20,000 times the Sun’s brightness. Because of its great mass, it’s already nearing the end of its life, even though it’s billions of years younger than the Sun. Before long, it will explode as a supernova. The Moon sometimes passes in front of the star because Pi Scorpii lies near the ecliptic – the Sun’s path across the sky. The Moon’s orbit around Earth is tilted a bit, so it roams a few degrees either side of the ecliptic. That allows it to occult quite a few stars that are bright enough to see with the unaided eye. This month alone, in fact, the Moon will stage almost a dozen occultations. But each of them is visible across only a small slice of the globe, so we don’t see all of them from here in the United States. But some of them align just right – allowing us to see the Moon briefly stomp out a star. The occultation of Pi Scorpii will be visible across almost all of the Lower 48 states. The exact time, and how long the star remains blocked, depends on your location. We’ll talk about the Moon and the heart of the scorpion tomorrow. Script by Damond Benningfield